Skip To The Main Content

PDA Glossary

PDA Glossary of Pharmaceutical and Biotechnology Terminology

PDA Technical Reports are highly valued membership benefits because they offer expert guidance and opinions on important scientific and regulatory topics and are used as essential references by industry and regulatory authorities around the world. These reports include terms which explain the material and enhance the reader’s understanding.

The database presented here includes the glossary terms from all current technical reports. The database is searchable by keyword, topic, or by technical report. Each definition provided includes a link to the source technical report within the PDA Technical Report Portal.

Browse Terms by Title


Browse Terms by TR #

  • Laminar Flow

    Type of fluid (gas or liquid) movement in which the fluid travels smoothly (in a nonturbulent way) or in regular paths. The velocity, pressure, and other flow properties at each point in the fluid remain constant. (TR69)

  • Largest Daily Dose

    Maximum daily dose of the next product to be produced in the equipment train. (TR70)

  • Latent Virus

    Latency is the ability of a virus to be dormant (latent) within a cell (for example, genetic episomes; provirus). Under certain conditions the virus may become active and produce particles. (TR71)

  • LD50/LC50

    Median lethal dose or median lethal concentration, of a toxin, radiation, or pathogen is the dose required to kill half the members of a tested population after specified test duration. LD50 figures are frequently used as a general indicator of a substance’s acute toxicity. (TR55)

  • Leachable

    A chemical component that migrates from a contact surface into a drug product or process fluid during storage or normal use conditions. The term leachable is often erroneously used to describe an extractable. (TR14) (TR26)

    Leachables are organic and inorganic chemical entities that migrate from a packaging/delivery system, packaging component, or packaging material of construction into an associated drug product under normal conditions of storage and use or during accelerated drug product stability studies. Leachables are typically a subset of extractables or are derived from extractables. (TR54-4)

    Chemical substances that are leached, from product-contact or non-product-contact materials, under typical process conditions and detected in final dosage. Leachables may be a subset of extractables, and can include their reaction or breakdown products. (TR66)

    Organic or inorganic chemical entity that migrates from pharmaceutical container closure system components into a drug product formulation. (TR73)

  • Leak Rate

    Leak rate is the quantity of air leakage over time into the sterilizer chamber obtained while performing a chamber leak test. The leak rate should not exceed a level that will inhibit the sterilization process during air removal or vacuum drying stages. (TR03)

  • Leak Test

    See System Integrity Test. (TR61)

  • Lenticular Filters

    A filter made up of a series of biconvex cells that are stacked on top of one another with rings between them to prevent bypass between the cells. End-caps are then placed at the top and bottom of the assembly and are held in place with a central core. [Synonyms: Lenticular Cartridge, Modules, Filter Elements, Filter Devices] (TR45)

  • Life Supporting or Life Sustaining Drug

    Life supporting or life sustaining is used to describe a product that is essential to, or that yields information that is essential to, the restoration or continuation of a bodily function that is important to the continuation of human life. (TR68)

  • Lifecycle

    All phases in the life of a product from the initial development through marketing until the product’s discontinuation. (TR54) (TR60)

    All phases in the life of a product, from the initial development through marketing until the prod­uct is discontinued. (TR60-2)

  • Ligand

    A functional molecule (small molecule or protein) coupled to the chromatography resin that selectively interacts with the target protein, impurities, or other molecules from the process stream. (TR14)

  • Limit

    A value for a residue above which a cleaning process would not be acceptable. (TR29) A value for a residue above which a cleaning validation protocol would fail. (TR49)

  • Limit of Detection (LOD)

    The lowest concentration of microorganisms in a test sample that can be detected, but not necessarily quantified, under the stated experimental conditions. (TR33)

    The lowest amount of analyte in a sample that can be distinguished from the absence of analyte. (TR41)

    The lowest concentration of analyte that can be unambiguously detected in a sample. For qualitative and for quantitative NAT methods, this value is conventionally expressed as a 95% positive cut-off value, representing the target concentration detected in 95% of repeated tests using a certain assay. (TR50)

  • Limit of Quantification

    The lowest number of microorganisms in a test sample that can be enumerated with acceptable accuracy and precision under the stated experimental conditions. (TR33)

  • Limit Sample

    An actual physical unit that is agreed to between the drug manufacturer and the glass manufacturer that defines the approximate maximum degree of acceptability for a specified non-conformance. Creation of limit samples between the user and the manufacturer is optional. (TR43)

  • Limit Test

    A quantitative test designed to give a positive/negative response. Ideally, a limit test has a high degree of specificity and a low limit of detection. (TR50).

  • Limit, Detection (DL)

    The lowest amount of analyte in a sample that can be detected but not necessarily quantitated as an exact value by an individual analytical procedure. [Synonym: Limit of detection (LOD)] (TR57)

  • Limit, Quantitation (QL)

    The lowest amount of analyte is a sample that can be quantitatively determined with suitable precision and accuracy by an individual analytical procedure. [Synonym: Limit of quantitation (LOQ)] (TR57)

  • Limiting Dilution

    In the context of this Technical Report the limiting dilution technique is used for virus cloning. The virus suspension is diluted until virus is no longer detectable. The dilution immediately before the dilution where infection of cells is no longer detectable is considered to contain only one virus particle or a very low number of virus particles. (TR47)

  • Limulus Amebocyte Lysate (LAL) Test

    Endotoxin detection and quantitation can be accomplished at high sensitivity and specificity using reagents manufactured from Limulus Amebocyte Lysate, a biological reagent prepared from horseshoe crabs and offered in a variety of formulations. (TR45)

  • Limulus Amoebocyte Lysate (LAL) Test

    A biologically based assay for the detection and quantitation of bacterial endotoxin. (TR69)

  • Linearity

    The ability to elicit results that are proportional to the concentration of microorganisms present in the sample within a given range, where accuracy and precision are demonstrated. (TR33)

    The linearity of an analytical procedure is its ability (within a given range) to obtain test results that are directly proportional to the concentration (amount) of analyte in the sample. (TR57)

  • Lipopolysaccharide

    A component of the cell wall of Gram-negative bacteria.(TR3)

    Component of the outer cell wall of Gram-negative bacteria that is pyrogenic. (TR69)(TR82)

  • Liquid Load

    A load consisting of closed containers of aqueous liquids. The sterilization of the container contents is achieved through transfer of energy through the container into the aqueous liquid. (TR01) (TR30) (TR48)

  • Load Density

    The amount of target molecules per volume of resin (e.g., gram protein per milliliter resin). (TR14)

  • Load Monitor

    A chemical, physical or biological indicator that provides an indication that a load was exposed to moist heat processing conditions. Note: In the United States, the load monitor must consist of a device in the form of a chemical, physical or biological indicator that is capable of direct measurement, or if appropriate, an indirect measurement of physical lethality delivered to the load. (TR30)

  • Load Zone

    Area within the sterilization chamber where materials to be sterilized may be placed. (TR01) (TR3) (TR48)

  • Loft

    Thickness of an air-filled insulation material. (TR72)

  • Log Partition or Partition Coefficient

    The partition coefficient is a ratio of concentrations of un-ionized compound between the two solutions usually water and octanol. To measure the partition coefficient of ionizable solutes, the pH of the aqueous phase is adjusted such that the predominant form of the compound is un-ionized. The logarithm of the ratio of the concentration of the un-ionized solute in the solvents is called log P; The log P values is also known as a measure of lipophilicity. (TR55)

  • Log Reduction

    Log reduction is defined as the first log being 90%, the second log being 9% and the third log being 0.09% of the original inoculums. (TR70)

  • Log Reduction Value (LRV)

    The logarithm to the base 10 of the ratio of organisms in the feed to organisms in the filtrate. (i.e., Log10(109/2) = 9.7). [Synonym: Log Titer Reduction] (TR45)

    Titer Reduction (TR) expressed as a base 10 logarithm. (TR75)

  • Log Titer Reduction (LTR) or Log Reduction Value (LRV)

    The virus reduction factor of an individual purification or inactivation step is defined as the log10 of the ratio of the virus titer or total load in the prepurification material and the virus titer or load in the post-purification material which is ready for use in the next step of the process. (TR41)

  • Logistics Service Providers (ISP or 3PIs)

    Freight forwarders and brokers that assist in moving the product, but may not physically touch the product. (TR52)

  • Lost Work Day (LWD)

    A day on which an employee does not work because of injury in a work-related accident. (TR52)

  • Lot or Batch

    A specific quantity of material produced in a process or series of processes so that it is expected to be homogeneous within specified limits.(TR76)

  • Low Endotoxin Recovery (LER)

    The inability to recover ≥50% activity over time when known amount of endotoxin is added to an undiluted product. LER cannot be overcome by dilution.(TR82)

  • Lyophilized (Product Cake)

    Freeze-dried product typically in the form of a solid plug or cake in the container. (TR79)